The invention relates to a piano sostenuto assembly for a grand piano.
In a piano, sound is created when a pianist presses upon a piano key, lifting a damper off a tensioned string and triggering a hammer to strike the tensioned string. When the piano key is released, the damper lowers to contact the string and stop the string from vibrating. If the pianist wishes to prevent the damper from lowering when the piano key is released, a damper pedal is pressed to raise and hold all of the string dampers lifted from their respective strings. Alternatively, the pianist can press a sostenuto pedal to hold already raised dampers in their lifted positions, leaving remaining dampers in contact upon the strings.
Referring to FIG. 1, when a pianist at a prior art grand piano presses down on a piano key 25, a soft key end felt 26 is raised (arrow 26a) into contact with an underlever 17 associated with the particular key 25. The motion of the piano key acts to raise the underlever (arrow 17a) and the topflange 15 attached to the underlever. A damper head 11 is associated with each underlever 17. A damper wire 13 connecting topflange 15 to damper head 11 transmits the upward motion of topflange 15 to damper head 11 to raise damper head 11 off of a tensioned string 12. The upward motion of underlever 17 is limited by contact of underlever 17 with a felt pad 24 of a damper stop rail 22.
To disengage all of the damper heads 11 from their respective strings 12, the pianist depresses a damper pedal 33, which acts through a series of connections (indicated generally at 30) to cause a damper tray 27 to move upward (arrow 27a), contacting and raising each of the underlevers 17. The motion of the underlevers is transmitted to the damper heads as described above.
Referring to FIG. 2A, also representing prior art, once in a lifted position, individual or multiple dampers can be held in elevated position by depressing a sostenuto pedal 52. The motion of pedal 52 causes a rod 51 attached to pedal 52 to be raised, causing a sostenuto pedal lever 50 to pivot about a connection point 53 (arrow 54) lowering a connecting rod 48 (shown in dashed line). Referring also to FIG. 2B, a sostenuto rail 40, mounted to an action frame 110 (FIG. 1) of the piano by a bracket 112, clamp 112a and bolt 112b, is connected to an end piece 48a of rod 48 by a wire loop 49 which is engaged in notch 48b and secured to the end piece 148a by clamp 49a and bolt 49b. Rail 40 is free to rotate within a curved section 112c of bracket 112 but is prevented from moving vertically.
The motion of rod 48 causes sostenuto rail 40 to be rotated about pivot point 56 (arrow 58). Rotation of sostenuto rail 40 causes a rail blade 41 to engage the underside 60 of a felt covered latch surface, tab nose 47, of all lifted topflanges 15 (shown in dashed line). Rail 40 acts to hold the raised damper head(s) off string 12 after key 25 has been released.
Referring again to FIG. 2A, tab nose 47 extends from a damper lever tab 42 pivotally mounted to topflange 15 by a center pin 43. A wire spring 45 biases tab 42 upward toward engagement with a stop felt 46. This arrangement permits the tab to be immovable in the upward direction but flexible in the downward direction. As a result, the pivoting sostenuto blade 41 can capture any designated damper in the lifted position while allowing uncaptured dampers to move freely upward, pushing their downwardly flexible tabs against the lower surface of the extended sostenuto blade. The newly raised damper is then captured in the lifted position.